Just in case anyone missed it, BMW released a sound clip of the M performance 328i exhaust..

Once you go to the link, click drivetrain, then click the exhaust pic in the top middle, below the picture of the exhaust you will see a 1/3, click the next button to hear a sound clip of the M performance exhaust (2/3), if you go to 3/3 you will hear a comparative clip of the 328i stock exhaust.

Any good grease monkey can do it, auspuffs are relatively straightforward. I used a BMW specialist Midas dealership in Brisbane to do my Remus exhaust on the E82 and they did a great job.

The trick is sourcing it for a globally competitive price, BMW Australia rips us on M Performance gear prices, for example I think the M Perf BBK weighs in at something like $6.5k locally compared to $2.1k plus tax and shipping from the US.